This invention relates generally to gasification systems and, more particularly, to systems and methods for capturing a rich carbon dioxide (CO2) stream produced by gasification systems.
At least some known gasification systems, such as those used in power plants, are integrated with at least one power-producing turbine system, thereby forming an integrated gasification combined-cycle (IGCC) power generation system. For example, at least some known gasification systems convert a mixture of fuel, air or oxygen (O2), steam, and/or carbon dioxide (CO2) into a synthetic gas, or “syngas.” The syngas is channeled to the combustor of a gas turbine engine, which powers a generator that supplies electrical power to a power grid. Exhaust from at least some known gas turbine engines is supplied to a heat recovery steam generator that generates steam for driving a steam turbine. Power generated by the steam turbine also drives an electrical generator that provides electrical power to the power grid.
At least some known gasification systems associated with IGCC systems initially produce a “raw” syngas fuel includes carbon monoxide (CO), hydrogen (H2), hydrogen sulfide (H2S), and/or carbon dioxide (CO2). Hydrogen sulfide is commonly referred to as an acid gas. Acid gases are generally removed from the raw syngas fuel to produce a “clean” syngas fuel used for combustion within the gas turbine engines. At least some known acid gas removal is performed with an acid gas removal subsystem that includes at least one main absorber that removes a majority of the H2S.
At least some known gasification systems also include at least one sulfur recovery unit (SRU) that recovers sulfur from the acid gas. Tail gas produced by the SRU is compressed and/or recycled to a gasification reactor using a tail gas unit (TGU). However, such a sulfur recovery system, including the SRU and TGU, represents a significant portion of the capital cost of an IGCC system. Moreover, when an IGCC power plant incorporates pre-combustion CO2 separation and purification systems, a significant additional capital cost is incurred.